Ordering federal prosecutors on Friday to crack down on drug offenders, Atty. Gen. Jeff Sessions made clear he wants the Justice Department to turn the clock back to an earlier, tougher era in the four-decades-long war on drugs.

In a memo, Sessions said federal prosecutors should “charge and pursue the most serious, readily provable offense” in drug cases, even when that would trigger mandatory minimum sentencing.

Mandatory sentencing laws for drug users have been controversial for years, and many Republicans as well as Democrats now oppose them as unfair, ineffective and too costly.

The new Justice Department policy cancels the Obama administration’s attempts to pull back on harsh sentencing strategies, which had produced a huge growth in prison populations. It restores some language from a 2003 memo written by then-Atty. Gen. John Ashcroft.

Speaking Friday at the Justice Department, Sessions said the crackdown was “a key part of President Trump’s promise to keep America safe,” linking drug trafficking to increased homicide rates in some cities.

“We are returning to the enforcement of the law as passed by Congress — plain and simple,” Sessions said.

Sessions rescinded policy memos signed in 2013 and 2014 by then-Atty. Gen. Eric H. Holder Jr. that instructed prosecutors to reserve the toughest charges for high-level traffickers and violent criminals.

Since then, the number of drug offenders given mandatory minimum sentences has dropped dramatically, contributing to a 14% decline in the total federal prison population, with 188,797 inmates this month.

Holder slammed Sessions’ policy Friday, calling it “ideologically motivated” and not supported by facts.“The policy announced today is not tough on crime,” Holder said. “It is dumb on crime.”

The new policy threatens to halt a push for bipartisan criminal justice reform that has been led by some of Trump’s closest advisors and embraced by key Republicans on Capitol Hill, including House Speaker Paul D. Ryan.

Sen. Rand Paul, (R-Ky.) criticized the new policy Friday, arguing that mandatory minimum sentences disproportionately targeted minorities because of how different drugs are categorized under the law.

The “new policy will accentuate that injustice,” Paul said in a statement.

“Sessions is an outlier in his own party and even among many of his own colleagues in the administration,” said Inimai Chettiar, a director at the Brennan Center for Justice at NYU School of Law in New York. “A lot of Republicans support reductions in sentencing.”

“I would say that we need to adopt criminal justice reform nationally. We have got to do a better job recognizing and correcting the errors in the system that do reflect institutional bias in criminal justice,” Pence said in a campaign debate last year.

As governor of Texas, Energy Secretary Rick Perry guided his state through a major shift in sentencing away from the kind of harsh penalties that Sessions seeks to restore in federal courts.

In those states and others, alarm at the escalating cost of incarceration helped drive calls for reform.

But Sessions, a former federal prosecutor in Alabama, was never on board with the push.As a U.S. senator from Alabama, he helped kill a proposed sentencing reform bill, warning the legislation could lead to more felons on the streets. He also helped block a 2016 bill that would have eased federal sentencing for marijuana use.

Since joining the Trump administration, Sessions has reversed an Obama administration attempt to phase out federal contracts with private prisons, saying the cells will be needed for the boost in inmate population he sees coming.

Under mandatory sentencing laws, judges have little discretion on how to sentence drug offenders. Prosecutors’ decisions on charging often determine how long offenders will spend in prison.

For example, if federal prosecutors include the amount of drugs in their written charges, that can trigger a mandatory minimum sentence.

They also can file motions for so-called sentence enhancements, which can effectively double drug sentences for repeat offenders, or put them in jail for life.

Some prosecutors use these tough tools as a hammer in plea negotiations, or to force offenders to cooperate.

In his memo, Sessions said prosecutors must disclose “all facts” relevant to a sentence, like drug amounts. He also canceled a Holder policy that said prosecutors should not use sentencing enhancement motions to coerce guilty pleas.

“Drug trafficking is an inherently violent business,” Sessions said. “If you want to collect a drug debt, you can’t file a lawsuit in court. You collect it by the barrel of a gun.”

He said heroin is cheaper, purer and more easily available than ever. Advocates of sentencing reform say that the opioid crisis is evidence that tough policies of the past have failed.

But Sessions said that tougher enforcement could “reverse that trend.”

One former federal judge from Tennessee said he was forced to sentence a low-level drug dealer to life in prison. The defendant refused to take a plea deal for 20 years in prison and was convicted at trial.

“Under no circumstances was this sentence justice,” said the former judge, Kevin Sharp, who has become an advocate for sentencing reform. “We ruined his life.”

In drug cases, Sharp said, the judge’s role in sentencing is dramatically reduced. “I have yet to talk to a judge who says mandatory minimums are a good idea,” he said.